Intersil HIP6004D Buck and synchronous-rectifier pwm controller and output voltage monitor Datasheet

HIP6004D
TM
Data Sheet
April 2000
Buck and Synchronous-Rectifier (PWM)
Controller and Output Voltage Monitor
The HIP6004D provides complete control and protection for
a DC-DC converter optimized for high-performance
microprocessor applications. It is designed to drive two
N-Channel MOSFETs in a synchronous-rectified buck
topology. The HIP6004D integrates all of the control, output
adjustment, monitoring and protection functions into a single
package.
The output voltage of the converter is easily adjusted and
precisely regulated. The HIP6004D includes a fully TTLcompatible 5-input digital-to-analog converter (DAC) that
adjusts the output voltage from 1.1VDC to 1.85VDC in 25mV
increments steps. The precision reference and voltage-mode
regulator hold the selected output voltage to within ±1% over
temperature and line voltage variations.
File Number
4855
Features
• Drives Two N-Channel MOSFETs
• Operates from +5V or +12V Input
• Simple Single-Loop Control Design
- Voltage-Mode PWM Control
• Fast Transient Response
- High-Bandwidth Error Amplifier
- Full 0% to 100% Duty Ratio
• Excellent Output Voltage Regulation
- ±1% Over Line Voltage and Temperature
• TTL-Compatible 5-Bit Digital-to-Analog Output
Voltage Selection
- 25mV Binary Steps . . . . . . . . . 1.100VDC to 1.850VDC
• Power-Good Output Voltage Monitor
The HIP6004D provides simple, single feedback loop,
voltage-mode control with fast transient response. It includes
a 200kHz free-running triangle-wave oscillator that is
adjustable from below 50kHz to over 1MHz. The error
amplifier features a 15MHz gain-bandwidth product and
6V/µs slew rate which enables high converter bandwidth for
fast transient performance. The resulting PWM duty ratio
ranges from 0% to 100%.
• Over-Voltage and Over-Current Fault Monitors
- Does Not Require Extra Current Sensing Element,
Uses MOSFET’s rDS(ON)
The HIP6004D monitors the output voltage with a window
comparator that tracks the DAC output and issues a Power
Good signal when the output is within ±10%. The HIP6004D
protects against over-current and overvoltage conditions by
inhibiting PWM operation. Additional built-in overvoltage
protection triggers an external SCR to crowbar the input
supply. The HIP6004D monitors the current by using the
rDS(ON) of the upper MOSFET which eliminates the need for
a current sensing resistor.
Applications
Ordering Information
PART NUMBER
HIP6004DCB
TEMP.
RANGE (oC)
0 to 70
PACKAGE
20 Ld SOIC
PKG.
NO.
M20.3
NOTE: When ordering, use the entire part number. Add the suffix T
to obtain the part in tape and reel, e.g., HIP6004DCB-T.
• Small Converter Size
- Constant Frequency Operation
- 200kHz Free-Running Oscillator Programmable from
50kHz to over 1MHz
• Power Supply for K7™, and Other Microprocessors
• High-Power DC-DC Regulators
• Low-Voltage Distributed Power Supplies
Pinout
HIP6004D
(SOIC)
TOP VIEW
VSEN
1
OCSET
2
19 OVP
SS
3
18 VCC
VID0
4
17 LGATE
VID1
5
16 PGND
VID2
6
15 BOOT
VID3
7
14 UGATE
VID4
8
13 PHASE
COMP
9
12 PGOOD
FB 10
1
20 RT
11 GND
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil and Design is a trademark of Intersil Corporation. | Copyright © Intersil Corporation 2000
K7™ is a trademark of Advanced Micro Devices, Inc.
HIP6004D
Typical Application
+12V
VCC
VIN = +5V OR +12V
HIP6004D
PGOOD
OCSET
MONITOR AND
PROTECTION
SS
EN
OVP
BOOT
RT
VID0
VID1
VID2
VID3
VID4
OSC
UGATE
PHASE
+VOUT
D/A
FB
-
LGATE
+
+
-
PGND
VSEN
COMP
GND
Block Diagram
VCC
VSEN
POWER-ON
RESET (POR)
110%
+
-
PGOOD
90%
+
-
OVERVOLTAGE
115%
10µA
+
OVP
-
SOFTSTART
+
-
OCSET
REFERENCE
200µA
OVERCURRENT
SS
BOOT
4V
UGATE
PHASE
VID0
VID1
VID2
VID3
VID4
TTL D/A
CONVERTER
(DAC)
PWM
COMPARATOR
DACOUT
+
-
+
-
ERROR
AMP
FB
GATE
INHIBIT CONTROL
LOGIC
PWM
LGATE
PGND
COMP
GND
OSCILLATOR
RT
2
HIP6004D
Absolute Maximum Ratings
Thermal Information
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +15V
Boot Voltage, VBOOT - VPHASE . . . . . . . . . . . . . . . . . . . . . . . . +15V
Input, Output or I/O Voltage . . . . . . . . . . . .GND -0.3V to VCC +0.3V
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class 2
Thermal Resistance (Typical, Note 1)
θJA (oC/W)
SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
110
SOIC Package (with 3in2 of Copper) . . . . . . . . . . . .
86
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 150oC
Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300oC
(SOIC - Lead Tips Only)
Operating Conditions
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . +12V ±10%
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . 0oC to 70oC
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE:
1. θJA is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
Recommended Operating Conditions, Unless Otherwise Noted
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
UGATE and LGATE Open
-
5
-
mA
Rising VCC Threshold
VOCSET = 4.5V
-
-
10.4
V
Falling VCC Threshold
VOCSET = 4.5V
8.2
-
-
V
-
1.26
-
V
VCC SUPPLY CURRENT
Nominal Supply
ICC
POWER-ON RESET
Rising VOCSET Threshold
OSCILLATOR
Free Running Frequency
RT = OPEN
185
200
215
kHz
Total Variation
6kΩ < RT to GND < 200kΩ
-15
-
+15
%
-
1.9
-
VP-P
∆VOSC
Ramp Amplitude
RT = Open
REFERENCE AND DAC
DAC (VID0-VID4) Input Low Voltage
-
-
0.8
V
DAC (VID0-VID4) Input High Voltage
2.0
-
-
V
DACOUT Voltage Accuracy
-1.0
-
+1.0
%
-
88
-
dB
ERROR AMPLIFIER
DC Gain
Gain-Bandwidth Product
GBWP
-
15
-
MHz
-
6
-
V/µs
350
500
-
mA
-
5.5
10
Ω
300
450
-
mA
-
3.5
6.5
Ω
-
115
120
%
VOCSET = 4.5VDC
170
200
230
µA
VSEN = 5.5V, VOVP = 0V
60
-
-
mA
-
10
-
µA
VSEN Rising
106
-
111
%
Lower Threshold (VSEN/DACOUT)
VSEN Falling
89
-
94
%
Hysteresis (VSEN/DACOUT)
Upper and Lower Threshold
-
2
-
%
IPGOOD = -5mA
-
0.5
-
V
Slew Rate
SR
COMP = 10pF
GATE DRIVERS
Upper Gate Source
IUGATE
VBOOT - VPHASE = 12V, VUGATE = 6V
Upper Gate Sink
RUGATE
ILGATE = 0.3A
Lower Gate Source
ILGATE
VCC = 12V, VLGATE = 6V
Lower Gate Sink
RLGATE
ILGATE = 0.3A
PROTECTION
Over-Voltage Trip (VSEN/DACOUT)
OCSET Current Source
IOCSET
OVP Sourcing Current
IOVP
Soft Start Current
ISS
POWER GOOD
Upper Threshold (VSEN/DACOUT)
PGOOD Voltage Low
VPGOOD
3
HIP6004D
Typical Performance Curves
80
CGATE = 3300pF
70
60
RT PULLUP
TO +12V
ICC (mA)
RESISTANCE (kΩ)
1000
100
50
CUPPER = CLOWER = CGATE
40
CGATE = 1000pF
30
10
20
RT PULLDOWN TO VSS
CGATE = 10pF
10
10
100
1000
0
100
200
300
SWITCHING FREQUENCY (kHz)
FIGURE 1. RT RESISTANCE vs FREQUENCY
Functional Pin Descriptions
400
500
600
700
800
900
1000
SWITCHING FREQUENCY (kHz)
FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY
VSEN
1
20 RT
(DACOUT). The level of DACOUT sets the converter output
voltage. It also sets the PGOOD and OVP thresholds. Table
1 specifies DACOUT for the all combinations of DAC inputs.
OCSET
2
19 OVP
COMP (Pin 9) and FB (Pin 10)
SS
3
18 VCC
VID0
4
17 LGATE
VID1
5
16 PGND
VID2
6
15 BOOT
VID3
7
14 UGATE
COMP and FB are the available external pins of the error
amplifier. The FB pin is the inverting input of the error
amplifier and the COMP pin is the error amplifier output.
These pins are used to compensate the voltage-control
feedback loop of the converter.
VID4
8
13 PHASE
COMP
9
12 PGOOD
FB 10
11 GND
GND (Pin 11)
Signal ground for the IC. All voltage levels are measured with
respect to this pin.
VSEN (Pin 1)
PGOOD (Pin 12)
This pin is connected to the converter’s output voltage. The
PGOOD and OVP comparator circuits use this signal to
report output voltage status and for overvoltage protection.
PGOOD is an open collector output used to indicate the
status of the converter output voltage. This pin is pulled low
when the converter output is not within ±10% of the
DACOUT reference voltage. Exception to this behavior is
the ‘11111’ VID pin combination which disables the
converter; in this case PGOOD asserts a high level.
OCSET (Pin 2)
Connect a resistor (ROCSET) from this pin to the drain of the
upper MOSFET. ROCSET, an internal 200µA current source
(IOCS), and the upper MOSFET on-resistance (rDS(ON)) set
the converter over-current (OC) trip point according to the
following equation:
I OCSET x R OCSET
I PEAK = ----------------------------------------------------r DS ( ON )
PHASE (Pin 13)
Connect the PHASE pin to the upper MOSFET source. This
pin is used to monitor the voltage drop across the MOSFET
for over-current protection. This pin also provides the return
path for the upper gate drive.
An over-current trip cycles the soft-start function.
UGATE (Pin 14)
SS (Pin 3)
Connect UGATE to the upper MOSFET gate. This pin
provides the gate drive for the upper MOSFET.
Connect a capacitor from this pin to ground. This capacitor,
along with an internal 10µA current source, sets the softstart interval of the converter.
VID0-4 (Pins 4-8)
VID0-4 are the input pins to the 5-bit DAC. The states of
these five pins program the internal voltage reference
4
BOOT (Pin 15)
This pin provides bias voltage to the upper MOSFET driver.
A bootstrap circuit may be used to create a BOOT voltage
suitable to drive a standard N-Channel MOSFET.
HIP6004D
PGND (Pin 16)
This is the power ground connection. Tie the lower MOSFET
source to this pin.
LGATE (Pin 17)
Connect LGATE to the lower MOSFET gate. This pin
provides the gate drive for the lower MOSFET.
VCC (Pin 18)
Provide a 12V bias supply for the chip to this pin.
OVP (Pin 19)
increasing width that charge the output capacitor(s). This
interval of increasing pulse width continues to t2 . With sufficient
output voltage, the clamp on the reference input controls the
output voltage. This is the interval between t2 and t3 in Figure 3.
At t3 the SS voltage exceeds the DACOUT voltage and the
output voltage is in regulation. This method provides a rapid
and controlled output voltage rise. The PGOOD signal toggles
‘high’ when the output voltage (VSEN pin) is within ±10% of
DACOUT. The 2% hysteresis built into the power good
comparators prevents PGOOD oscillation due to nominal
output voltage ripple.
The OVP pin can be used to drive an external SCR in the
event of an overvoltage condition. Output rising 15% more
than the DAC-set voltage triggers a high output on this pin
and disables PWM gate drive circuitry.
PGOOD
(2V/DIV.)
0V
RT (Pin 20)
This pin provides oscillator switching frequency adjustment.
By placing a resistor (RT) from this pin to GND, the nominal
200kHz switching frequency is increased according to the
following equation:
SOFT-START
(1V/DIV.)
OUTPUT
VOLTAGE
(1V/DIV.)
6
5 x 10
Fs ≈ 200kHz + --------------------R T ( kΩ )
(RT to GND)
0V
0V
t1
Conversely, connecting a pull-up resistor (RT) from this pin
to VCC reduces the switching frequency according to the
following equation:
t2
t3
TIME (5ms/DIV.)
FIGURE 3. SOFT START INTERVAL
7
Functional Description
Initialization
The HIP6004D automatically initializes upon receipt of power.
Special sequencing of the input supplies is not necessary. The
Power-On Reset (POR) function continually monitors the input
supply voltages. The POR monitors the bias voltage at the VCC
pin and the input voltage (VIN) on the OCSET pin. The level on
OCSET is equal to VIN less a fixed voltage drop (see overcurrent protection). The POR function initiates soft start
operation after both input supply voltages exceed their POR
thresholds. For operation with a single +12V power source, VIN
and VCC are equivalent and the +12V power source must
exceed the rising VCC threshold before POR initiates operation.
Soft Start
The POR function initiates the soft start sequence. An internal
10µA current source charges an external capacitor (CSS) on
the SS pin to 4V. Soft start clamps the error amplifier output
(COMP pin) and reference input (+ terminal of error amp) to the
SS pin voltage. Figure 3 shows the soft start interval with
CSS = 0.1µF. Initially the clamp on the error amplifier (COMP
pin) controls the converter’s output voltage. At t1 in Figure 3, the
SS voltage reaches the valley of the oscillator’s triangle wave.
The oscillator’s triangular waveform is compared to the ramping
error amplifier voltage. This generates PHASE pulses of
5
Over-Current Protection
The over-current function protects the converter from a
shorted output by using the upper MOSFET’s on-resistance,
rDS(ON) to monitor the current. This method enhances the
converter’s efficiency and reduces cost by eliminating a
current sensing resistor.
SOFT-START
(RT to 12V)
4V
2V
0V
OUTPUT INDUCTOR
4 x 10
Fs ≈ 200kHz – --------------------R T ( kΩ )
15A
10A
5A
0A
TIME (20ms/DIV.)
FIGURE 4. OVER-CURRENT OPERATION
The over-current function cycles the soft-start function in a
hiccup mode to provide fault protection. A resistor (ROCSET)
programs the over-current trip level. An internal 200µA current
sink develops a voltage across ROCSET that is referenced to
VIN . When the voltage across the upper MOSFET (also
HIP6004D
referenced to VIN) exceeds the voltage across ROCSET, the
over-current function initiates a soft-start sequence. The softstart function discharges CSS with a 10µA current sink and
inhibits PWM operation. The soft-start function recharges
CSS , and PWM operation resumes with the error amplifier
clamped to the SS voltage. Should an overload occur while
recharging CSS , the soft start function inhibits PWM operation
while fully charging CSS to 4V to complete its cycle. Figure 4
shows this operation with an overload condition. Note that the
inductor current increases to over 15A during the CSS
charging interval and causes an over-current trip. The
converter dissipates very little power with this method. The
measured input power for the conditions of Figure 4 is 2.5W.
The over-current function will trip at a peak inductor current
(IPEAK) determined by:
I OCSET x R OCSET
I PEAK = ----------------------------------------------------r DS ( ON )
where IOCSET is the internal OCSET current source (200µA
typical). The OC trip point varies mainly due to the
MOSFET’s rDS(ON) variations. To avoid over-current tripping
in the normal operating load range, find the ROCSET resistor
from the equation above with:
1. The maximum rDS(ON) at the highest junction temperature.
2. The minimum IOCSET from the specification table.
3. Determine IPEAK for I PEAK > I OUT ( MAX ) + ( ∆I ) ⁄ 2 ,
where ∆I is the output inductor ripple current.
For an equation for the ripple current see the section under
component guidelines titled ‘Output Inductor Selection’.
A small ceramic capacitor should be placed in parallel with
ROCSET to smooth the voltage across ROCSET in the
presence of switching noise on the input voltage.
Output Voltage Program
The output voltage of a HIP6004D converter is programmed
to discrete levels between 1.100VDC and 1.850VDC . The
voltage identification (VID) pins program an internal voltage
reference (DACOUT) with a TTL-compatible 5-bit digital-toanalog converter (DAC). The level of DACOUT also sets the
PGOOD and OVP thresholds. Table 1 specifies the DACOUT
voltage for the 32 different combinations of connections on the
VID pins. The output voltage should not be adjusted while the
converter is delivering power. Remove input power before
changing the output voltage. Adjusting the output voltage
during operation could toggle the PGOOD signal and exercise
the overvoltage protection.
‘11111’ VID pin combination resulting in a 0V output setting
activates the Power-On Reset function and disables the gate
drives circuitry. For this specific VID combination, though,
PGOOD asserts a high level. This unusual behavior has been
implemented in order to allow for operation in dualmicroprocessor systems where AND-ing of the PGOOD
signals from two individual power converters is implemented.
Application Guidelines
Layout Considerations
As in any high frequency switching converter, layout is very
important. Switching current from one power device to another
can generate voltage transients across the impedances of the
interconnecting bond wires and circuit traces. These
interconnecting impedances should be minimized by using
wide, short printed circuit traces. The critical components
should be located as close together as possible, using ground
plane construction or single point grounding.
TABLE 1. OUTPUT VOLTAGE PROGRAM
PIN NAME
PIN NAME
VID4
VID3
VID2
VID1
VID0
NOMINAL OUTPUT
VOLTAGE DACOUT
VID4
VID3
VID2
VID1
VID0
NOMINAL OUTPUT
VOLTAGE DACOUT
1
1
1
1
1
0
0
1
1
1
1
1.475
1
1
1
1
0
1.100
0
1
1
1
0
1.500
1
1
1
0
1
1.125
0
1
1
0
1
1.525
1
1
1
0
0
1.150
0
1
1
0
0
1.550
1
1
0
1
1
1.175
0
1
0
1
1
1.575
1
1
0
1
0
1.200
0
1
0
1
0
1.600
1
1
0
0
1
1.225
0
1
0
0
1
1.625
1
1
0
0
0
1.250
0
1
0
0
0
1.650
1
0
1
1
1
1.275
0
0
1
1
1
1.675
1
0
1
1
0
1.300
0
0
1
1
0
1.700
1
0
1
0
1
1.325
0
0
1
0
1
1.725
1
0
1
0
0
1.350
0
0
1
0
0
1.750
1
0
0
1
1
1.375
0
0
0
1
1
1.775
1
0
0
1
0
1.400
0
0
0
1
0
1.800
1
0
0
0
1
1.425
0
0
0
0
1
1.825
1
0
0
0
0
1.450
0
0
0
0
0
1.850
NOTE: 0 = connected to GND or VSS , 1 = connected to VDD through pull-up resistors.
6
HIP6004D
PWM
COMPARATOR
HIP6004D
LO
PHASE
CIN
Q2
LGATE
D2
LO
-
∆VOSC
Q1
DRIVER
+
CO
ESR
(PARASITIC)
ZFB
-
ZIN
+
REFERENCE
ERROR
AMP
RETURN
FIGURE 5. PRINTED CIRCUIT BOARD POWER AND
GROUND PLANES OR ISLANDS
DETAILED COMPENSATION COMPONENTS
ZFB
C2
Figure 5 shows the critical power components of the converter.
To minimize the voltage overshoot the interconnecting wires
indicated by heavy lines should be part of ground or power
plane in a printed circuit board. The components shown in
Figure 5 should be located as close together as possible.
Please note that the capacitors CIN and CO each represent
numerous physical capacitors. Locate the HIP6004D within 3
inches of the MOSFETs, Q1 and Q2 . The circuit traces for the
MOSFETs’ gate and source connections from the HIP6004D
must be sized to handle up to 1A peak current.
Figure 6 shows the circuit traces that require additional
layout consideration. Use single point and ground plane
construction for the circuits shown. Minimize any leakage
current paths on the SS pin and locate the capacitor, CSS
close to the SS pin because the internal current source is
only 10µA. Provide local VCC decoupling between VCC and
GND pins. Locate the capacitor, CBOOT as close as practical
to the BOOT and PHASE pins.
D1
CBOOT
LO
VOUT
+12V
Q2
CO
LOAD
PHASE
VCC
SS
CVCC
CSS
GND
FIGURE 6. PRINTED CIRCUIT BOARD SMALL SIGNAL
LAYOUT GUIDELINES
Feedback Compensation
Figure 7 highlights the voltage-mode control loop for a
synchronous-rectified buck converter. The output voltage
(VOUT) is regulated to the Reference voltage level. The
error amplifier (Error Amp) output (VE/A) is compared with
the oscillator (OSC) triangular wave to provide a pulsewidth modulated (PWM) wave with an amplitude of VIN at
the PHASE node.
7
C1
VOUT
ZIN
C3
R2
R3
R1
COMP
FB
+
HIP6004D
DACOUT
FIGURE 7. VOLTAGE-MODE BUCK CONVERTER
COMPENSATION DESIGN
The PWM wave is smoothed by the output filter (LO and CO).
The modulator transfer function is the small-signal transfer
function of VOUT/VE/A . This function is dominated by a DC
Gain and the output filter (LO and CO), with a double pole
break frequency at FLC and a zero at FESR . The DC Gain of
the modulator is simply the input voltage (VIN) divided by the
peak-to-peak oscillator voltage ∆VOSC .
Modulator Break Frequency Equations
+VIN
Q1
CO
VE/A
PGND
BOOT
VOUT
PHASE
VOUT
LOAD
UGATE
HIP6004D
VIN
DRIVER
OSC
VIN
1
F LC = ------------------------------------------2π x L O x C O
1
F ESR = -------------------------------------------2π x ESR x C O
The compensation network consists of the error amplifier
(internal to the HIP6004D) and the impedance networks ZIN
and ZFB. The goal of the compensation network is to provide
a closed loop transfer function with the highest 0dB crossing
frequency (f0dB) and adequate phase margin. Phase margin
is the difference between the closed loop phase at f0dB and
180 degrees. The equations below relate the compensation
network’s poles, zeros and gain to the components (R1 , R2 ,
R3 , C1 , C2 , and C3) in Figure 7. Use these guidelines for
locating the poles and zeros of the compensation network:
1.
2.
3.
4.
5.
6.
7.
Pick Gain (R2/R1) for desired converter bandwidth.
Place 1ST Zero Below Filter’s Double Pole (~75% FLC).
Place 2ND Zero at Filter’s Double Pole.
Place 1ST Pole at the ESR Zero.
Place 2ND Pole at Half the Switching Frequency.
Check Gain against Error Amplifier’s Open-Loop Gain.
Estimate Phase Margin - Repeat if Necessary.
HIP6004D
Compensation Break Frequency Equations
1
F Z1 = -----------------------------------2π x R 2 x C 1
1
F P1 = -------------------------------------------------------- C 1 x C 2
2π x R 2 x  ----------------------
 C1 + C2 
1
F Z2 = ------------------------------------------------------2π x ( R 1 + R 3 ) x C 3
1
F P2 = -----------------------------------2π x R 3 x C 3
Figure 8 shows an asymptotic plot of the DC-DC converter’s
gain vs frequency. The actual Modulator Gain has a high gain
peak due to the high Q factor of the output filter and is not
shown in Figure 8. Using the above guidelines should give a
Compensation Gain similar to the curve plotted. The open
loop error amplifier gain bounds the compensation gain.
Check the compensation gain at FP2 with the capabilities of
the error amplifier. The Closed Loop Gain is constructed on
the log-log graph of Figure 8 by adding the Modulator Gain (in
dB) to the Compensation Gain (in dB). This is equivalent to
multiplying the modulator transfer function to the
compensation transfer function and plotting the gain.
The compensation gain uses external impedance networks
ZFB and ZIN to provide a stable, high bandwidth (BW) overall
loop. A stable control loop has a gain crossing with
-20dB/decade slope and a phase margin greater than 45
degrees. Include worst case component variations when
determining phase margin.
Modern microprocessors produce transient load rates above
1A/ns. High frequency capacitors initially supply the transient
and slow the current load rate seen by the bulk capacitors.
The bulk filter capacitor values are generally determined by
the ESR (Effective Series Resistance) and voltage rating
requirements rather than actual capacitance requirements.
High frequency decoupling capacitors should be placed as
close to the power pins of the load as physically possible. Be
careful not to add inductance in the circuit board wiring that
could cancel the usefulness of these low inductance
components. Consult with the manufacturer of the load on
specific decoupling requirements.
Use only specialized low-ESR capacitors intended for
switching-regulator applications for the bulk capacitors. The
bulk capacitor’s ESR will determine the output ripple voltage
and the initial voltage drop after a high slew-rate transient. An
aluminum electrolytic capacitor’s ESR value is related to the
case size with lower ESR available in larger case sizes.
However, the Equivalent Series Inductance (ESL) of these
capacitors increases with case size and can reduce the
usefulness of the capacitor to high slew-rate transient loading.
Unfortunately, ESL is not a specified parameter. Work with
your capacitor supplier and measure the capacitor’s
impedance with frequency to select a suitable component. In
most cases, multiple electrolytic capacitors of small case size
perform better than a single large case capacitor.
Output Inductor Selection
100
FZ1 FZ2
FP1
FP2
80
OPEN LOOP
ERROR AMP GAIN
GAIN (dB)
60
40
20
20LOG
(R2/R1)
0
20LOG
(VIN/∆VOSC)
MODULATOR
GAIN
-20
CLOSED LOOP
GAIN
FLC
-60
10
100
∆I =
COMPENSATION
GAIN
-40
1K
FESR
10K
100K
1M
VIN - VOUT
Fs x L
x
VOUT
VIN
∆VOUT = ∆I x ESR
Increasing the value of inductance reduces the ripple current
and voltage. However, the large inductance values reduce
the converter’s response time to a load transient.
10M
FREQUENCY (Hz)
FIGURE 8. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
Component Selection Guidelines
Output Capacitor Selection
An output capacitor is required to filter the output and supply
the load transient current. The filtering requirements are a
function of the switching frequency and the ripple current.
The load transient requirements are a function of the slew
rate (di/dt) and the magnitude of the transient load current.
These requirements are generally met with a mix of
capacitors and careful layout.
8
The output inductor is selected to meet the output voltage
ripple requirements and minimize the converter’s response
time to the load transient. The inductor value determines the
converter’s ripple current and the ripple voltage is a function
of the ripple current. The ripple voltage and current are
approximated by the following equations:
One of the parameters limiting the converter’s response to
a load transient is the time required to change the inductor
current. Given a sufficiently fast control loop design, the
HIP6004D will provide either 0% or 100% duty cycle in
response to a load transient. The response time is the time
required to slew the inductor current from an initial current
value to the transient current level. During this interval the
difference between the inductor current and the transient
current level must be supplied by the output capacitor.
Minimizing the response time can minimize the output
capacitance required.
The response time to a transient is different for the
application of load and the removal of load. The following
HIP6004D
equations give the approximate response time interval for
application and removal of a transient load:
tRISE =
L x ITRAN
VIN - VOUT
tFALL =
L x ITRAN
VOUT
where: ITRAN is the transient load current step, tRISE is the
response time to the application of load, and tFALL is the
response time to the removal of load. With a +5V input
source, the worst case response time can be either at the
application or removal of load and dependent upon the
DACOUT setting. Be sure to check both of these equations
at the minimum and maximum output levels for the worst
case response time. With a +12V input, and output voltage
level equal to DACOUT, tFALL is the longest response time.
Input Capacitor Selection
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use small ceramic
capacitors for high frequency decoupling and bulk capacitors
to supply the current needed each time Q1 turns on. Place the
small ceramic capacitors physically close to the MOSFETs
and between the drain of Q1 and the source of Q2 .
The important parameters for the bulk input capacitor are the
voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and current
ratings above the maximum input voltage and largest RMS
current required by the circuit. The capacitor voltage rating
should be at least 1.25 times greater than the maximum
input voltage and a voltage rating of 1.5 times is a
conservative guideline. The RMS current rating requirement
for the input capacitor of a buck regulator is approximately
1/2 the DC load current.
voltage-current transitions and do not adequately model power
loss due the reverse-recovery of the lower MOSFET’s body
diode. The gate-charge losses are dissipated by the HIP6004D
and don't heat the MOSFETs. However, large gate-charge
increases the switching interval, tSW which increases the upper
MOSFET switching losses. Ensure that both MOSFETs are
within their maximum junction temperature at high ambient
temperature by calculating the temperature rise according to
package thermal-resistance specifications. A separate heatsink
may be necessary depending upon MOSFET power, package
type, ambient temperature and air flow.
PUPPER = Io2 x rDS(ON) x D +
PLOWER = Io2 x rDS(ON) x (1 - D)
Where: D is the duty cycle = VOUT / VIN ,
tSW is the switch ON time, and
FS is the switching frequency.
Standard-gate MOSFETs are normally recommended for
use with the HIP6004D. However, logic-level gate MOSFETs
can be used under special circumstances. The input voltage,
upper gate drive level, and the MOSFET’s absolute gate-tosource voltage rating determine whether logic-level
MOSFETs are appropriate.
Figure 9 shows the upper gate drive (BOOT pin) supplied by a
bootstrap circuit from VCC. The boot capacitor, CBOOT
develops a floating supply voltage referenced to the PHASE
pin. This supply is refreshed each cycle to a voltage of VCC
less the boot diode drop (VD) when the lower MOSFET, Q2
turns on. Logic-level MOSFETs can only be used if the
MOSFET’s absolute gate-to-source voltage rating exceeds
the maximum voltage applied to VCC.
For a through hole design, several electrolytic capacitors may
be needed. For surface mount designs, solid tantalum
capacitors can be used, but caution must be exercised with
regard to the capacitor surge current rating. These capacitors
must be capable of handling the surge-current at power-up.
Some capacitor series available from reputable manufacturers
are surge current tested.
+12V
DBOOT
VCC
BOOT
9
CBOOT
UGATE
Q1
PHASE
-
+
In high-current applications, the MOSFET power dissipation,
package selection and heatsink are the dominant design
factors. The power dissipation includes two loss components;
conduction loss and switching loss. The conduction losses are
the largest component of power dissipation for both the upper
and the lower MOSFETs. These losses are distributed between
the two MOSFETs according to duty factor (see the equations
below). Only the upper MOSFET has switching losses, since
the Schottky rectifier clamps the switching node before the
synchronous rectifier turns on. These equations assume linear
+5V OR +12V
+ VD -
HIP6004D
MOSFET Selection/Considerations
The HIP6004D requires 2 N-Channel power MOSFETs. These
should be selected based upon rDS(ON) , gate supply
requirements, and thermal management requirements.
1 Io x V x t
IN SW x FS
2
LGATE
PGND
NOTE:
VG-S ≈ VCC -VD
Q2
D2
NOTE:
VG-S ≈ VCC
GND
FIGURE 9. UPPER GATE DRIVE - BOOTSTRAP OPTION
Figure 10 shows the upper gate drive supplied by a direct
connection to VCC . This option should only be used in
converter systems where the main input voltage is +5VDC or
less. The peak upper gate-to-source voltage is approximately
VCC less the input supply. For +5V main power and +12VDC
HIP6004D
Schottky Selection
for the bias, the gate-to-source voltage of Q1 is 7V. A logiclevel MOSFET is a good choice for Q1 and a logic-level
MOSFET can be used for Q2 if its absolute gate-to-source
voltage rating exceeds the maximum voltage applied to VCC .
Rectifier D2 is a clamp that catches the negative inductor
swing during the dead time between turning off the lower
MOSFET and turning on the upper MOSFET. The diode
must be a Schottky type to prevent the lossy parasitic
MOSFET body diode from conducting. It is acceptable to
omit the diode and let the body diode of the lower MOSFET
clamp the negative inductor swing, but efficiency will drop
one or two percent as a result. The diode’s rated reverse
breakdown voltage must be greater than the maximum
input voltage.
+12V
+5V OR LESS
VCC
BOOT
HIP6004D
Q1
UGATE
PHASE
+
Figure 11 shows an application circuit of a DC-DC Converter
for a microprocessor. Detailed information on the circuit,
including a complete Bill-of-Materials and circuit board
description, can be found in Application Note AN9672.
Although the Application Note details the HIP6004, the same
evaluation platform can be used to evaluate the HIP6004D.
Intersil AnswerFAX (321-724-7800) Doc. #99672.
D2
Q2
LGATE
-
HIP6004D DC-DC Converter Application
Circuit
NOTE:
VG-S ≈ VCC -5V
PGND
NOTE:
VG-S ≈ VCC
GND
FIGURE 10. UPPER GATE DRIVE - DIRECT VCC DRIVE OPTION
VIN =
+5V
OR
+12V
L1 - 1µH
F1
2 x 1µF
2N6394
CIN
5x 1000µF
+12V
2K
D1
0.1µF
1000pF
VCC
18
2 OCSET
MONITOR
AND
PROTECTION
SS 3
0.1µF
OVP
19
1K
12 PGOOD
15 BOOT
VSEN 1
RT 20
VID0
VID1
VID2
VID3
VID4
FB
4
5
6
7
8
0.1µF
OSC
14 UGATE
Q1
L2
3µH
13 PHASE
HIP6004D
D/A
-
10
17 LGATE
+
+
-
2.2nF
Q2
16 PGND
9
COMP
+VOUT
D2
COUT
9x 1000µF
11
GND
20K
8.2nF
0.1µF
1.33K
15
Component Selection Notes:
COUT - Each 1000µF 6.3W VDC, Sanyo MV-GX or Equivalent.
CIN - Each 330µF 25W VDC, Sanyo MV-GX or Equivalent.
L2 - Core: Micrometals T50-52B; Winding: 10 Turns of 16AWG.
L1 - Core: Micrometals T50-52; Winding: 5 Turns of 18AWG.
D1 - 1N4148 or Equivalent.
D2 - 3A, 40V Schottky, Motorola MBR340 or Equivalent.
Q1 , Q2 - Intersil MOSFET; RFP70N03.
FIGURE 11. MICROPROCESSOR DC-DC CONVERTER
10
HIP6004D
Small Outline Plastic Packages (SOIC)
M20.3 (JEDEC MS-013-AC ISSUE C)
20 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE
N
INDEX
AREA
H
0.25(0.010) M
B M
INCHES
E
-B1
2
3
L
SEATING PLANE
-A-
h x 45o
A
D
-C-
e
A1
B
0.25(0.010) M
C
0.10(0.004)
C A M
SYMBOL
MIN
MAX
MIN
MAX
NOTES
A
0.0926
0.1043
2.35
2.65
-
A1
0.0040
0.0118
0.10
0.30
-
B
0.013
0.0200
0.33
0.51
9
C
0.0091
0.0125
0.23
0.32
-
D
0.4961
0.5118
12.60
13.00
3
E
0.2914
0.2992
7.40
7.60
4
e
α
B S
0.050 BSC
1.27 BSC
-
H
0.394
0.419
10.00
10.65
-
h
0.010
0.029
0.25
0.75
5
L
0.016
0.050
0.40
1.27
6
N
NOTES:
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication Number 95.
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
3. Dimension “D” does not include mold flash, protrusions or gate burrs.
Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006
inch) per side.
4. Dimension “E” does not include interlead flash or protrusions. Interlead
flash and protrusions shall not exceed 0.25mm (0.010 inch) per side.
5. The chamfer on the body is optional. If it is not present, a visual index
feature must be located within the crosshatched area.
6. “L” is the length of terminal for soldering to a substrate.
7. “N” is the number of terminal positions.
8. Terminal numbers are shown for reference only.
9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater
above the seating plane, shall not exceed a maximum value of
0.61mm (0.024 inch)
10. Controlling dimension: MILLIMETER. Converted inch dimensions
are not necessarily exact.
MILLIMETERS
α
20
0o
20
8o
0o
7
8o
Rev. 0 12/93
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Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
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11
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